Catalytic reforming of petroleum hydrocarbons



J. A. E. MOY 2,852,442

Sept. 16, 1958 CATALYTIC REFQRMING oF PETROLEUM HYDRocARBoNs 2sheets-sheet 1 Filed Sept. l1, 1956 .futur-.xm

Sept. 16, 1958 J. A. E.A MOY 2,852,442

CATALYTIC REFORMING oF PETROLEUM HYDRocARBoNs Filed sept. 11, 195e 2sheets-sheet 2 arMQ/ M y 2,852,442 Patented Sept. 16, 1958 tliceCATALYTIC REFORMING F PETROLEUM HYDRCARBONS John Arthur Edgar Moy,Sunbury-on-Thames, England, assignor to The British Petroleum CompanyLimited, London, England, a British joint-stock corporation ApplicationSeptember 11, 1956, Serial No. 609,146

Claims priority, application Great Britain September 23, 1955 6 Claims.(Cl. 196-50) This invention relates to the catalytic reforming processwhich, as applied to petroleum hydrocarbons, consists in contacting thehydrocarbons at elevated temperature and pressure with a catalyst forthe various chemical reactions which contribute to the production ofaromatics whereby a product of increased aromatic content as cornparedwith the feedstock is obtained.

The catalytic reforming process is particularly useful in the petroleumindustry for treating naphtha fractions of low aromatic content and lowoctane number for the production of naphthas having increased aromaticcontent and higher octane number and therefore more suitable for use asmotor gasolines. One such process which has been developed is thePlatforming process in which a catalyst is used comprising a smallamount of platinum, and sometimes a halogen, supported on an aluminabase. In order to obtain a product of still higher octane number, it hasrecently been proposed to subject the initial reformate to solventextraction to produce an extract rich in aromatics, the raitinate beingreturned to the reforming zone.

The present invention relates to a process of this latter kind and hasamong its objects to obtain a product having an aromatic content of70-80% The process according to the present invention comprisescontacting a catalytic reformer feedstock with liquid sulphur dioxide inconventional manner for the production of an aromatic extract and araffinate, passing the -ratlnate to a catalytic reforming zone for theproduction of aromatics, contacting the product from the catalyticreforming zone with liquid sulphur dioxide in conventional manner forthe production of an aromatic extract of the same aromatic content asthe aromatic extract previously referred to, and a rainate, and passingthe rafnate to the catalytic reforming zone together with the rainatepreviously referred to.

Extraction of aromatics from the naphtha feedstock is advantageous fortwo reasons: (a) an increased quantity of aromatics can be formed byincreased dehydrocyclization of parains, (b) there is a reduction inquantity of unreactive compounds passing through the catalytic reformingprocess.

Extraction of aromatics from the catalytic reformate is a more eiectivemethod of obtaining a iinal product of the required aromatic contentthan is the operation of the catalytic reforming process at higherseverity which would result in rapid deactivation of the catalyst.

The production of aromatic extracts of the same aromatic content may beaccomplished by operating at the same temperature but with differentsolvent to oil ratios. This method of operation has the followingadvantages:

(a) The two extraction towers can be made as one column with twocompartments.

(b) Only one system of ranate phase evaporators and one system ofextract phase evaporators are required since the relevant phases arecombined.

A product of still greater aromatic content may be obtained according toa further feature of the invention component and recycled to theextraction towers.

by contacting countercurrently the aromatic extracts referred to abovein solution in liquid sulphur dioxide with a non-aromatic hydrocarboncut having a different boiling range from the extracts, whereby some ofthe nonaromatics present in the extracts are replaced by nonaromatics ofdifferent boiling range which may subsequently be removed bydistillation, yielding a product of still greater aromatic content of upto Operation in this manner enables a highly aromatic extract to beproduced economically. Production of such an extract by a conventionalsolvent extraction process would entail the use of a very low extractiontemperature, about -70 F., which would present problems in the materialsof construction and would also be expensive. Furthermore, the washingoperation may be conveniently carried out at the same temperature as thesolvent extraction stages referred to, so that all three operations canbe carried out in a single column having three compartments.

Two methods of carrying the invention into effect will.

now be described with reference to Figures l and 2 respectively of theaccompanying drawings. Referring iirst to Figure l, the feedstock, forexample a naphtha boiling in the range 90 to 190 C. and containing 12 to20% aromatics, is contacted countercurrently in a conventionalmultistage solvent extraction tower A at a temperature in the range 30to |20 F. with liquid sulphur dioxide in the proportion of 50 to 150volu-rnes of sulphur dioxide per volumes of naphtha. The solvent ratiois adjusted to give an extract containing the required concentration ofaromatics. The products from this operation are raffinate phase l andextract phase l.

Raflinate phase l is combined with raffinate phase 2 (as describedbelow) and is passed to a raffinate phase evaporating system C wheresulphur dioxide is removed from the substantially aromatic-free naphthaby distillation. tower.

The aromatic-free naphtha is passedto a catalytic -rei forming process Din which a product containing about 40 to 50% aromatics is made.

The stabilized reformate is passed to a second conventional multistagesolvent extraction tower B in which it is contacted countercurrently ata temperature in the range 30 to +20 F. with liquid sulphur dioxide inthe proportion of 200 to 400 volumes of sulphur dioxide per 100 volumesof reformate. The solvent ratio is adjusted to give an extractcontaining the required concentration of aromatics which is the sameconcentration as that obtained from the first extraction operation. Theproducts from this operation are ranate phase 2 and extract phase 2.

Raflinate phase 2 is combined with rainate phase l (as described above)before passing to the ratlinate phase evaporators C in which sulphurdioxide is removed from the substantially aromatic-free naphtha which isrecycled (with the dearomatized naphtha feedstock) to the reformingprocess.

Extract phase 2 is combined with extract phase 1 before passing to theextract phase evaporating system E where sulphur dioxide is removed fromthe hydrocarbon The hydrocarbon component is the desired productcontaining 70% to 80% aromatics.

Referring now to Figure 2, the operation is the same as described withreference to Figure 1 up to the point where extract phases 1 and 2 arecombined. The combined stream is then passed to a wash tower F where itis contacted countercurrently with a non-aromatic hydrocarbon cut whichboils outside the range of the extracted hydrocarbon, a de-aromatizedheavy kerosine but being preferred. The ratio of the volume of wash Thesulphur dioxide is recycled to the extractionl `oil to the volume ofhydrocarbons in the combined extract phase is in the range 0.25 to 1.5to 1. The Washing operation is carried out at the same temperature asthe solvent extraction stage. The product from this operation areratiinate phase 3 and extract phase 3.

Rainate phase 3 is passed to an evaporating system G where sulphurdioxide is distilled off and recycled to the extraction towers A and B,while the hydrocarbon part of the ratllnate phase is fed to a ratlinatesplitter H. The splitter will give material in the naphtha boiling rangeas an overhead product which is recycled to the extraction tower A, andkerosine as a bottoms product which is recycled to the wash tower F.

Extract phase 3 Ais passed to an evaporating system I Where sulphurdioxide is distilled off and recycled to extraction towers A and B,while the hydrocarbon part of the extract phase is fed to an extractsplitter K. The splitter will give as an overhead product the requiredproduct containing 95% aromatics, and kerosine as a bottoms productwhich is recycled to the Wash tower F.

I claim:

l. A process for the catalytic reforming of a petroleum feedstock, whichcomprises contacting the feedstock with liquid sulphur dioxide for theproduction of an aromatic extract and a ranate, passing the rai'linateVto a catalytic reforming zone for the production of aromatics,contacting the product from the catalytic reforming zone with liquidsulphur dioxide for the production of an aromatic extract and araffinate, the contacting of the feedstock and the contacting of theproduct of the catalytic reforming zone with liquid sulphur dioxidebeing carried out at the same temperature but with different solvent tooil ratios to give aromatic extracts of the same aromatic content, andpassing the raflinate to the catalytic reforming zone together with therafnate previously referred to.

2. A process according to claim 1, wherein the feedstock consists of anaphtha fraction.

3. A process according to claim 2, wherein the naphtha fraction iscontacted at a temperature in the range 30 to +20 F. with liquid sulphurdioxide in the proportion of 50 to 150 volumes of sulphur dioxide per100 volumes of naphtha.

4. A process according to claim 2, wherein the product of the catalyticreforming zone is contacted at a temperature in the range 30 to +20 F.with liquid sulphur dioxide in the proportion of 200 to 400 volumes ofsulphur dioxide per 100 volumes of product.

5. A process for the catalytic reforming of a petroleum feedstock, whichcomprises contacting the feedstock with liquid sulphur dioxide for theproduction of an aromatic extract and a ratiinate, passing the raiiinateto a catalytic reforming zone for the production of aromatics,'contacting the product from the catalytic reforming zone with liquidsulphur dioxide for the production of an aromatic extract of the samearomatic content as the aromatic extract previously referred to, passingthe ratnate to the catalytic reforming zone together with the raffinatepreviously referred to, combining said aromatic extracts, contacting thecombined extracts, in solution in liquid sulphur dioxide,countercurrently with a dearomatised heavy kerosine fraction, the ratioof said kerosine fraction to the hydrocarbons in the combined extractsbeing in the range of 0.25 to 1.5 :1 by volume, and distilling theextracts after being thus contacted for the recovery of a product ofincreased aromatic content.

6. A process according to claim 5, wherein said contacting with adearomatized heavy kerosine fraction is carried out at the sametemperature as the solvent extraction stages.

References Cited in the le of this patent OTHER REFERENCES Oil and GasJournal, June 16, 1952, pp. 313, 316 (article by F, L. Resen) UNITEDSTATES PATENT oEEIcE CERTIFICATION 0F CORREC'IICN Patent No. 2,852,442September I6, 1958 John Arthur Edgar Moy It is hereby certified thaterror ppears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 3, line 34, before "raffinate" insert w last mentioned Signed andsealed this 13th day of June 1961 (SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting fficer Commissioner of Patents

1. A PROCESS FOR THE CATALYTIC REFORMING OF A PETROLEUM FEEDSTOCK, WHICHCOMPRISES CONTACTING THE FEEDSTOCK WITH LIQUID SULPHUR DIOXIDE FOR THEPRODUCTION OF AN AROMATIC EXTRACT AND A RAFFINATE, PASSING THE RAFFINATETO A CATALYTIC REFORMING ZONE FOR THE PRODUCTION OF AROMATICS CONTACTINGTHE PRODUCT FROM THE CATALYTIC REFORMING ZONE WITH LIQUID SULPHURDIOXIDE FOR THE PRODUCTION OF AN AROMATIC EXTRACT AND A RAFFINATE, THECONTACTING OF THE FEEDSTOCK AND THE CONTACTING OF THE PRODUCT OF THECATALYTIC REFORMING ZONE WITH LIQUID SULPHUR DIOXIDE BEING CARRIED OUTAT THE SAME TEMPERATURE BUT WITH DIFFERENT SOLVENT TO OIL RATIOS TO GIVEAROMATIC EXTRACTS OF THE SAME AROMATIC CONTENT, AND PASSING THERAFFINATE TO THE CATALYTIC REFORMING ZONE TOGETHER WITH THE RAFFINATEPREVIOUSLY REFERRED TO.
 2. A PROCESS ACCORDING TO CLAIN 1, WHEREIN THEFEEDSTOCK CONSISTS OF A NAPHTHA FRACTION.